FBI agents arrested the men November 1, identifying them as being part of a fringe militia group.

According to arrest affidavits filed in the case, Roberts and Thomas agreed to buy a silencer, a bomb and parts to convert a semi-automatic rifle to a fully automatic machine gun from an undercover agent.

"When it comes time to saving the Constitution, that means some people gotta die," an arrest affidavit quotes Thomas as saying during one recorded conversation.

Adams and Crump worked to obtain castor beans and produce the biotoxin ricin, a highly poisonous substance, an FBI agent states in the documents.

Meanwhile, a government informant recorded the men discussing their plans to manufacture ricin and attack Justice Department officials, federal judges and Internal Revenue Service agents.

Prosecutors said the public was never in imminent danger.

The affidavits don't identify the "known militia organization." But according to the documents, the men talked about spreading ricin across several cities at once, including Washington, Atlanta, New Orleans and Jacksonville, Florida. The fringe group called itself the "covert group," according to one affidavit.

According to the Southern Poverty Law Center, an organization based in Montgomery, Alabama, that works against racism and intolerance, the number of patriot and militia groups has soared since 2008, when the economy took a sharp downturn.

Mark Potok, head of the group's Intelligence Project, told CNN there's another factor.

"The appearance of Barack Obama on the scene ... for many of these people he really represents the changing racial demographics of the country," Potok said.

"At first you think it is another over-the-hill gang story," Potok said. "These old men sitting around ... making these plans. But according to authorities, they had taken a number of concrete steps to go ahead and actually make these things happen."

During an April meeting at his home, Thomas allegedly told participants he had a "bucket list" of politicians, government officials, corporate leaders and media figures he said should be targeted to "make the country right again."

"I could shoot ATF and IRS all day long. All the judges and the DOJ and the attorneys and prosecutors," the affidavit quotes Thomas as saying.

Crump allegedly said he wanted to make 10 pounds of ricin for distribution.

"Dump that little (unintelligible), that's all you gotta do is lay it in the damn road, the cars are gonna spread it," the affidavit quotes him as saying.

According to one of the affidavits, Crump formerly worked for a contractor doing "maintenance-type services" at the Centers for Disease Control and Prevention in Atlanta.

Crump also spoke of an even deadlier substance, "worse than anthrax," but the group would need financial backing to produce it, according to the affidavit.

The document states a castor bean provided to the informant by Adams and Crump tested positive for ricin.

The U.S. Agriculture Department verified Adams formerly worked at the Agriculture Research Service as a lab technician, an affidavit says.

According to another affidavit, Thomas allegedly said the group was ready to move forward with obtaining silencers from an active-duty member of the U.S. Army. In a phone call, he also said the four began physical training to prepare for their plans, the affidavit states.

U.S. Attorney Sally Quillian Yates told CNN Atlanta affiliate WXIA that the investigation began earlier this year when an informant talked with the FBI about conversations he had overheard. The informant taped conversations with the four suspects and an undercover agent began talking with them, Yates said.

"They had some of the (ricin) ingredients that were necessary but not all the ingredients," she said. "It's really important for the public to know and be assured that the FBI was on top of this and they were monitoring this every step of the way."

Discussions on how to spread the ricin included driving down an interstate highway and letting it waft out of a window, Yates told WXIA.

According to one affidavit, the confidential informant is on bond for pending felony state charges. An FBI polygrapher determined the individual "gave less than truthful responses concerning the activities of the militia group."

But, the affidavit states, the credibility of the informant has been demonstrated by the source's accurate recounting of the conversations the source recorded during meetings, "when compared to the audio and video recordings of the meetings and physical surveillance of those meetings conducted by law enforcement agents."

Adams, Crump and Roberts are from Toccoa, about 90 miles northeast of Atlanta, while Thomas is from nearby Cleveland, Georgia, prosecutors said.

Public records show no criminal records for Roberts, Crump, and Adams, while Thomas has only driving-related offenses.